1. Field of the Invention
The present invention relates to a light beam cut-off device which is applied to, for example, an image recording apparatus in which a light beam modulated by a light beam scanning device in accordance with image information is generated and a photosensitive material is exposed to the light beam to allow an image to be formed thereon, which light beam cut-off device cuts off the light beam at a position between the light beam scanning device and the photosensitive material at the time exposure for the photosensitive material is stopped.
2. Description of the Related Art
In recent years, a digital photographic printer (hereinafter referred to as xe2x80x9cphotographic printerxe2x80x9d) utilizing digital exposure has been put to practical use. In the photographic printer, a light beam modulated in accordance with digital image data is deflected by a light beam scanning device in a main scanning direction, and at the same time, a photosensitive material being conveyed in a sub-scanning direction is exposed by scanning to the light beam to allow an image (latent image) to be formed thereon. Thereafter, the photosensitive material is conveyed to a developing section and subjected therein to developing processing, and outputted as a print (photograph). In some of such photographic printers, roll paper in which an elongated photosensitive material is wound in the form of a roll is used to carry out printing processing and developing processing for the photosensitive material continuously for a long time. In the photographic printer in which roll paper is used as the photosensitive material, roll paper pulled out from a magazine is subjected to various processing including exposure, developing and drying while being conveyed along a predetermined conveying path, and cut out for each frame by a cutter provided in the vicinity of an exit of the developing section and made into photographic prints. The light beam scanning device used by such a photographic printer may be provided with a light source such as a laser diode (LD) for outputting a light beam, a main scanning means which deflects a light beam outputted from the light source and effects main scanning by the light beam on a photosensitive material, and an external modulator for modulating the light beam outputted from the light source based on an image signal.
In the aforementioned photographic printer, so long as a plurality of image signals each bearing an image are sequentially supplied without placing a waiting time therebetween, images can be sequentially recorded without stopping conveying of a photosensitive material. However, there is a possibility that an image signal which bears an image to be subsequently recorded is not immediately supplied at the time recording of a certain image is completed. In this case, generally, conveying of the photosensitive material is temporarily stopped so that the photosensitive material may not be wastefully consumed. However, in a case in which a light beam is modulated by an external modulator, if the photosensitive material is brought into a stopped state, a region of the photosensitive material with an image recorded thereon, or its vicinities may be affected by fogging. In other words, when the external modulator is used, a recording light source is generally brought into a state of being continuously turned on, and the extinction ratio of a light modulator such as an acousto-optic modulator (AOM) is about 1:1000. The light beam emitted from the recording light source in a state of being continuously turned on cannot be completely cut off, and therefore, the photosensitive material stopped at a fixed position is irradiated with the light beam. Although the light beam is very weak, a fixed region on the photosensitive material is continuously irradiated with the light beam during the photosensitive material being stopped, thereby causing fogging on the photosensitive material. Such fogging of the photosensitive material occurs not only in a blank region but also in an image region in accordance with a method for controlling conveying of the photosensitive material. As a result, the quality of a printed photographic image is considerably deteriorated.
Some of conventional light beam scanning devices applied to an image recording apparatus such as a photographic printer may include therein a mechanical shutter mechanism for a light beam so as to prevent the aforementioned fogging of a photosensitive material. Such a light beam scanning device is disclosed in, for example, Japanese Patent Application (JP-A) No. 9-121269. However, the mechanical shutter mechanism unavoidably generates a vibration and the vibration is transmitted to a light source or a main scanning means, which results in deterioration of image quality. Accordingly, the light beam scanning device needs to have a vibration cut-off structure which prevents transmission of a vibration from the shutter mechanism. However, the vibration cut-off structure is disposed in a narrow inner space of the apparatus and the structure becomes complicated.
Further, in a photographic printer in which an image is formed on a photosensitive material (sheet paper) previously in the shape of a sheet, sheet paper can be held at the upstream side of an exposure position at the time exposure by the light beam scanning device is stopped. Therefore, no shutter mechanism for preventing occurrence of fogging needs to be provided in the light beam scanning device. However, the light beam scanning device having no built-in shutter mechanism is not directly applied to a photographic printer in which an image is formed on an elongated photosensitive material (roll paper), and needs to be modified on a large scale. For this reason, the light beam scanning device cannot be shared between the photographic printer for forming an image on sheet material and the photographic printer for forming an image on roll paper. As a result, reduction in costs of the device cannot be facilitated.
In view of the aforementioned circumstances, it is an object of the present invention to provide a light beam cut-off (blocking) device which can be installed separately from a light beam scanning device and which can cut off a light beam emitted from the light beam scanning device immediately before a photosensitive material at the time exposure for the photosensitive material is stopped, and can prevent transmission of a vibration to the light beam scanning device.
In accordance with a first aspect of the present invention, there is provided a light beam cut-off device which comprises: a shutter member disposed between a light beam scanning device which emits a light beam, and a photosensitive material exposed to a light beam emitted from the light beam scanning device, and supported in a movable manner between a cut-off position at which an optical path of the light beam emitted from the light beam scanning device is cut off by the shutter member, and an open position at which the shutter member retreats from the optical path of the light beam emitted from the light beam scanning device; a shutter driving portion for moving the shutter member to the open position at the time the photosensitive material is exposed by the light beam scanning device, and moving the shutter member to the cut-off position at the time exposure for the photosensitive material is stopped; a chassis member on which the shutter member and the shutter driving portion are mounted; and a vibration cut-off portion which prevents transmission of a vibration from the chassis member to the light beam scanning device.
In accordance with a second aspect of the present invention, in the device of the first aspect, the light beam scanning device and the chassis member are supported by a supporting structure, the vibration cut-off portion is disposed at least one of between the chassis member and the supporting structure and between the light beam scanning device and the supporting structure.
In accordance with a third aspect of the present invention, in the device according to one of the first and second aspects, the shutter member is formed into an elongated plate extending in a main scanning direction in which the light beam is deflected by the light beam scanning device, and is supported swingably around a supporting shaft provided at one end thereof in a widthwise direction between the cut-off position and the open position.
In accordance with a fourth aspect of the present invention, in the device according to one of the first to third aspects, the chassis member has a cooling fan mounted thereon, the cooling fan cooling the shutter driving portion by air flow generated thereby and restraining a change of temperature in a space including the optical path of the light beam emitted from the light beam scanning device.
In accordance with a fifth aspect of the present invention, the device according to one of the first to fourth aspects further comprises a position sensor for detecting the shutter member located at one of the cut-off position and the open position; a setting section for setting a moving amount of the shutter member, by which the shutter member detected by the position sensor and located at the one of the cut-off position and the open position reaches the other of the cut-off position and the open position; and a shutter control section for controlling the shutter driving portion so that the shutter member moves by the moving amount of the shutter member, which is set by the setting section, when the shutter member moves from the one of the cut-off position and the open position to the other.
In accordance with a sixth aspect of the present invention, in the device according to the first aspect, the light beam scanning device and the chassis member are respectively supported by supporting structures, the vibration cut-off portion is disposed between the supporting structures.
In accordance with a seventh aspect of the present invention, there is provided a light beam cut-off device which comprises: a shutter member disposed outside of a light beam scanning device which emits a light beam and between the light beam scanning device and a photosensitive material exposed by a light beam emitted from the light beam scanning device, and supported in a movable manner between a cut-off position at which an optical path of the light beam emitted from the light beam scanning device is cut off by the shutter member, and an open position at which the shutter member retreats from the optical path of the light beam emitted from the light beam scanning device; a shutter driving portion for moving the shutter member to the open position at the time the photosensitive material is exposed by the light beam scanning device, and moving the shutter member to the cut-off position at the time exposure for the photosensitive material is stopped; and a chassis member on which the shutter member and the shutter driving portion are mounted, wherein the shutter member is formed into an elongated plate extending in a main scanning direction in which the light beam is deflected by the light beam scanning device, and is supported swingably around a supporting shaft provided at one end thereof in a widthwise direction between the cut-off position and the open position.
In accordance with an eighth aspect of the present invention, in the device according to the seventh aspect, the device further comprises a vibration cut-off portion which prevents transmission of a vibration from the chassis member to the light beam scanning device.
In accordance with the light beam cut-off device of the present invention, first, at the time exposure for the photosensitive material is carried out, the shutter driving portion moves the shutter member to the open position at which the shutter member retreats from the optical path of the light beam emitted from the light beam scanning device. At the time exposure for the photosensitive material is stopped, the shutter member is moved to the cut-off position at which the optical path of the light beam emitted form the light beam scanning device is cut off. As a result, at the time exposure for the photosensitive material is carried out, the light beam emitted from the light beam scanning device is made incident on the photosensitive material without being cut off by the shutter member and the photosensitive material can be exposed to the light beam. Further, at the time exposure for the photosensitive material is stopped, even if the light beam is emitted from the light beam scanning device, the light beam is cut off by the shutter member located at the cut-off position. Accordingly, occurrence of fogging in the photosensitive material can be reliably prevented.
Further, the vibration cut-off portion prevents transmission of a vibration from the chassis member on which the shutter member and the shutter driving portion, which may generate vibratory force, are mounted, to the light beam scanning device. As a result, it is possible to prevent deterioration of image quality due to fluctuation of a light beam on the photosensitive material due to a vibration from the chassis member.
In a case in which the light beam scanning device and the chassis member are supported by a common supporting structure, the vibration cut-off portion can be constituted from a vibration absorber such as vibration-proof (isolation) rubber interposed between the chassis member and the supporting structure and/or between the light beam scanning device and the supporting structure. Further, in a case in which the light beam scanning device and the chassis member are respectively supported by physically separated supporting structures, the vibration absorber such as vibration-proof rubber may be interposed between the plurality of supporting structures.